A typical fluid electrolyte rechargeable battery, such as a flooded lead-acid battery, includes at least one battery cell with positive and negative electrodes and an electrolyte in which the electrodes are submerged. For example, a conventional 12-volt battery includes six 2-volt cells. Different battery applications may require different battery configurations. These types of batteries have a battery housing enclosing the battery cells that includes a port through which the electrolyte is supplied to the cells.
A battery of this type may be repeatedly discharged and charged to generate electrical energy, which makes the battery a suitable power source for many applications. For example, flooded lead-acid batteries may be used as power sources for electric vehicles, such as forklifts, golf cars, electric cars, and hybrid cars. These batteries are also used for emergency or standby power supplies, or to store power generated by photovoltaic systems.
For optimal performance, the electrodes are completely submerged in the electrolyte, which typically includes an aqueous acid solution. However, fluid is lost from the battery due to out-gassing during the charging of the battery, so replenishment of the fluid is necessary. For example, a fluid filing system may be connected to a fluid source every three to four weeks. However, one of the problems with this requirement is that a separate hook-up to a fluid source is required to replenish the fluid. Further, for optimal battery performance, it is necessary for a maintenance worker to perform this function at the correct point in the charging/discharging cycle of the battery before the fluid level is depleted too much. If this function is not performed at the correct time, battery life may be adversely affected.